The Krafla Geothermal Field, Iceland: 2. The natural state of the system

Bodvarsson, G.S.; Pruess, Karsten; Stefansson, V.; Eliasson, E.T.

doi:10.1029/wr020i011p01531

Cited by 31 publications

(15 citation statements)

References 7 publications

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“…B, developed from these temperature profiles in conjunction with variations in wellhead pressure, fluid chemistry, and well‐production characteristics such as transmissivity (Stefánsson ; Bödvarsson et al . ,b,c; Pruess et al . ; Ármannsson et al .…”

Section: Introductionmentioning

confidence: 99%

Hydrogeology of the Krafla geothermal system, northeast Iceland

et al. 2015

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The Krafla geothermal system is located in Iceland's northeastern neovolcanic zone, within the Krafla central volcanic complex. Geothermal fluids are superheated steam closest to the magma heat source, two‐phase at higher depths, and sub‐boiling at the shallowest depths. Hydrogen isotope ratios of geothermal fluids range from −87‰, equivalent to local meteoric water, to −94‰. These fluids are enriched in 18O relative to the global meteoric line by +0.5–3.2‰. Calculated vapor fractions of the fluids are 0.0–0.5 wt% (~0–16% by volume) in the northwestern portion of the geothermal system and increase towards the southeast, up to 5.4 wt% (~57% by volume). Hydrothermal epidote sampled from 900 to 2500 m depth has δD values from −127 to −108‰, and δ18O from −13.0 to −9.6‰. Fluids in equilibrium with epidote have isotope compositions similar to those calculated for the vapor phase of two‐phase aquifer fluids. We interpret the large range in δDEPIDOTE and δ18OEPIDOTE across the system and within individual wells (up to 7‰ and 3.3‰, respectively) to result from variable mixing of shallow sub‐boiling groundwater with condensates of vapor rising from a deeper two‐phase reservoir. The data suggest that meteoric waters derived from a single source in the northwest are separated into the shallow sub‐boiling reservoir, and deeper two‐phase reservoir. Interaction between these reservoirs occurs by channelized vertical flow of vapor along fractures, and input of magmatic volatiles further alters fluid chemistry in some wells. Isotopic compositions of hydrothermal epidote reflect local equilibrium with fluids formed by mixtures of shallow water, deep vapor condensates, and magmatic volatiles, whose ionic strength is subsequently derived from dissolution of basalt host rock. This study illustrates the benefits of combining phase segregation effects in two‐phase systems during analysis of wellhead fluid data with stable isotope values of hydrous alteration minerals when evaluating the complex hydrogeology of volcano‐hosted geothermal systems.

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Section: Introductionmentioning

confidence: 99%

Hydrogeology of the Krafla geothermal system, northeast Iceland

et al. 2015

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“…During the 1980s, MULKOM and TOUGH were applied extensively to geothermal reservoir studies, including natural state modeling (Bodvarsson et al, 1984b), design and analysis of well tests (Bodvarsson et al, 1984a), production and injection problems in producing geothermal fields (Pruess and Bodvarsson, 1984; Bodvarsson et al, 1987), and fundamental studies of geothermal reservoir dynamics (Pruess and Narasimhan, 1982, 1985; Pruess, 1985; O'Sullivan et al, 1985; Pruess et al, 1987). Geothermal applications remain a prominent area for TOUGH2 (O'Sullivan et al, 2001) and are covered in a special issue of the journal Geothermics , to be published in 2004.…”

Section: Historical Remarksmentioning

confidence: 99%

The TOUGH Codes—A Family of Simulation Tools for Multiphase Flow and Transport Processes in Permeable Media

Pruess

2004

Vadose Zone Journal

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Numerical simulation has become a widely practiced and accepted technique for studying flow and transport processes in the vadose zone and other subsurface flow systems. This article discusses a suite ,of codes developed primarily at Lawrence Berkeley National Laboratory with a capability to model multiphase flows with phase change. We s u m a r i z e history and goals in the development of the TOUGH codes, and present the governing equations for multiphase, multicomponent flow. Special emphasis is given to space discretization by means of integral finite differences (ED). Issues of code implementation and architecture are addressed, as are code applications, maintenance and h a r e developments.

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“…The study of fluid flow in hydrothermal systems has a long history in Iceland because geothermal energy is plentiful [ Flóvenz , 2008]. Consequently, major research efforts focus on understanding heat transfer and phase distribution in geothermal fields that are currently used for providing Iceland with energy [e.g., Bodvarsson et al , 1984a, 1984b, 1984c]. However, there is also long‐standing, more scientific interest in investigating the interaction between fluid flow and magmatic intrusions [c.f., Lowell , 1991; Driesner and Geiger , 2007; Ingebritsen et al , 2010] for which Iceland provides an excellent natural laboratory.…”

Section: Introductionmentioning

confidence: 99%

Hydrothermal fluid flow within a tectonically active rift‐ridge transform junction: Tjörnes Fracture Zone, Iceland

2010

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[1] We investigate the regional fluid flow dynamics in a highly faulted transform area, the Tjörnes Fracture Zone in northern Iceland which is characterized by steep geothermal gradients, hydrothermal activity, and strong seismicity. We simulate fluid flow within the Tjörnes Fracture Zone using a high-resolution model that was based on the available geological and geophysical data and has the aim to represent the complex geological structures and the thermodynamical processes that drive the regional fluid flow in a physically realistic way. Our results show that convective heat flow and mixing of cold and saline seawater with deep hydrothermal fluids controls the large-scale fluid flow. The distribution of faults has a strong influence on the local hydrodynamics by focusing flow around clusters of faults. This explains the nature of isolated upflow zones of hot hydrothermal fluids which are observed in the Tjörnes Fracture Zone. An important emergent characteristic of the regional fluid flow in the Tjörnes Fracture Zone are two separate flow systems: one in the sedimentary basins, comprising more vigorous convection, and one in the crystalline basement, which is dominated by conduction. These two flow systems yield fundamental insight into the connection between regional hydrothermal fluid flow and seismicity because they form the basis of a toggle switch mechanism that is thought to have caused the hydrogeochemical anomalies recorded at Húsavik before and after the 5.8 M earthquake in September 2002.

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The Krafla Geothermal Field, Iceland: 2. The natural state of the system

Cited by 31 publications

References 7 publications

Hydrogeology of the Krafla geothermal system, northeast Iceland

Hydrogeology of the Krafla geothermal system, northeast Iceland

The TOUGH Codes—A Family of Simulation Tools for Multiphase Flow and Transport Processes in Permeable Media

Hydrothermal fluid flow within a tectonically active rift‐ridge transform junction: Tjörnes Fracture Zone, Iceland

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